while we are at it, let's also fix the obvious design flaws in C and UNIX/LINUX, especially the huge number of unfortunately named functions and commands.
That's not the point. He said it wasn't possible to improve on the committee. But of course it is.
But while we're on the subject: both C and UNIX are actively being updated and improved even now. The Common Lisp standard hasn't changed in any significant way since the 1980s. In Lisp everyone is just adopting ad hoc standards, agreeing under the table that everyone should use a certain networking package, threading mechanism, or Unicode standard for Lisp characters. That's the worst of many possible ways to deal with the problem.
One can claim that C is best improved by replacing it with a new languages. See Rust, D, and others. Lisp, too. -> Clojure, Julia, Racket, ...
The 'step 1' 'take Common Lisp' is already hopeless, because there are few people interested in that for various reasons.
I don't think it's 'trivial' to fix a fading large niche language like Common Lisp, which was designed at a different time, with had much more design power back then. It's actually far from trivial.
But while we're on the subject: both C and UNIX are actively being updated and improved even now. The Common Lisp standard hasn't changed in any significant way since the 1980s. In Lisp everyone is just adopting ad hoc standards, agreeing under the table that everyone should use a certain networking package, threading mechanism, or Unicode standard for Lisp characters. That's the worst of many possible ways to deal with the problem.